1. Field of the Invention
The present invention relates to a lid unit for a thin-plate supporting container for use in storing or transporting thin plates such as semiconductor wafers, storage disks, liquid crystal glass substrates or the like, or for use in production processes of the thin plates.
2. Description of the Related Art
Thin-plate supporting containers for storage or transportation of thin plates such as semiconductor wafers or the like received therein are generally known.
Such a thin-plate supporting container mainly includes a container body and a lid unit for closing an opening on the top of the container body. In the container body, various members are provided to support thin plates such as semiconductor wafers or the like. The thin-plate supporting container must be transported with its interior maintained clean in order to prevent contamination of the surfaces of the thin plates such as the semiconductor wafers or the like received in the container. Hence, the container is hermetically sealed; that is, a lid unit is fixed to the container body for purposes of hermetical sealing. A variety of structures is known which can fix the lid unit to the container body.
The thin-plate supporting container transported to a plant for producing semiconductors or the like is placed on a production line where the lid unit is automatically attached or detached by the use of a specific apparatus.
A lid unit cooperative with the above specific apparatus is disclosed in Japanese Patent Laid-Open No. 2001-512288. As shown in FIG. 2 of the accompanying drawings, a lid unit 1 includes a main body 2, a cam member 3, a latch arm 4 and a fulcrum 5.
The cam member 3 is rotationally attached to the main body 2 and has a cam portion 6. The cam portion 6 is provided with a joint opening 7 in the shape of an elongated hole.
The latch arm 4 is provided at its proximal portion with an S-shaped cam follower portion 8, and the follower portion 8 is fitted to and caught in the joint opening 7.
The fulcrum 5 has a projecting member located on the main body 2 and supports the latch arm 4.
In this arrangement, when the cam member 3 rotates, the S-shaped cam follower 8 caught in the joint opening 7 is pressed upwardly while it is moving rightwards as seen in FIG. 2. Thus, the latch arm 4 rotates about the fulcrum 5 while it is extending from the main body 2 so that the extremity of the latch arm 4 is pressed downwardly.
At this time, the extremity of the latch arm 4 has fitted in a hole of the container body, and upon downward movement of the latch arm 4, the lid unit is pressed toward and fixed to the container body.
In the above-mentioned lid unit 1, the latch arm 4 extends from the main body 2 and fits at its extremity in the hole on the container body side. It is necessary, however, that the lid unit be placed in pressed condition with respect to the container body such that the latch arm 4 is allowed to extend from the main body 2. This is because a sealing member is disposed between the lid unit and the container body to seal the container body hermetically. The sealing member is formed from a synthetic resin or the like and is of a resilient character, and hence, pushes back the lid unit having fitted in the container body. Thus, the lid unit should be placed in pressed condition toward the container body to extend the latch arm 4 from the main body 2.
In this instance, when an attempt is made to attach the lid unit to the container body in a state in which the container body is oriented laterally (a state in which the semiconductor wafers or the like are oriented in the horizontal direction), the container body results in displacement. In attaching of the lid unit to the container body, the lid unit should be maintained in pressed condition toward the container body as noted above. However, the container body when oriented laterally becomes displaced since it has nothing that holds the container body. This leaves a problem in that it is difficult to achieve automatic attachment and detachment of the lid unit.